tools: update eslint config

This makes sure the eslint config is up to date for eslint 6.0.0.

PR-URL: https://github.com/nodejs/node/pull/27670


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>